This invention relates to security systems, and in particular to a method and apparatus for increasing the number of wireless devices/identification codes to which a wired or wireless security system will respond.
FIG. 1 illustrates a typical wired security system 10 of the prior art comprising a central control unit 12, a central transceiver 14, a console display/keypad 18, a plurality of remote sensors 20 and local sensors 22, a telephone dialer 24 and a siren 26. The remote sensors 20 are hard-wired to the central transceiver 14, which communicates with the central control unit 12 via a system bus 28. The system bus 28 also links the central control unit 12 to the console display/keypad 18. The central control unit 12 is connected to the telephone dialer 24 and the siren 26 via an auxiliary local bus 30. The central control unit is also hardwired to the local sensors 22. Despite a lack of wireless capability (i.e., wireless communication between components, especially between the remote sensors 20 and the central control unit 12), this type of wired security system 10 prevails in a majority of commercial applications.
In contrast, a relatively recent innovation in security systems is a wireless security system 32 as illustrated in FIG. 2 in which wireless remote sensors 21 communicate with a wireless central receiver 15 in order to report their status to the central control unit 12. Wireless keys 34, which are small remote control devices, have become popular for remote arming and disarming of the wireless security system 32, as well as remote control of other devices via the wireless central receiver 15 and central control unit 12. As shown in FIG. 2, the conventional wireless security system 32 is substantially functionally the same as the wired security system 10 illustrated in FIG. 1, except that the wireless central receiver 15, an optional wireless central transmitter 17, and wireless remote sensors 21 have been substituted for their wired counterparts of FIG. 1. In addition, the wireless key 34 transmits control messages to the wireless central receiver 15. The wireless central receiver 15 transfers these control messages over the system bus 28 to the central control unit 12, which performs an appropriate action or function. Such appropriate action may involve the initiation of an alarm condition that then sounds the siren 26 and causes the telephone dialer 24 to automatically dial an appropriate number such as the police station or firehouse. Substantially any change in status of the wireless security system 32 would be displayed to the user on the console display/keypad 18.
One of the major advantages of a wireless security system is a reduction in installation time due to the fact that the wireless remote sensors 21 do not require wiring back to the wireless central receiver 15. However, the local bus 30 and the system bus 28 must still be hard-wired and the wireless central receiver 15. Wireless central transmitter 17 and console display/keypad 18 must be assigned unique system bus addresses to avoid contention on the shared system bus 28. In a similar manner, an identification code for each of the wireless remote sensors 21 as well as the wireless key 34 must be "learned" by the central control unit 12. The identification code 36, as illustrated in FIG. 6, represents a portion of a radio frequency or wireless message 38 transmitted by each of the wireless remote sensors 21 and wireless key 34, and is used to distinguish between them. The process of learning the identification codes (i.e. initializing the system) involves causing the wireless remote sensors 21 and the wireless key 34 to transmit their respective radio frequency message 38 while denoting the validity of the wireless message 38 received by depressing a button or buttons on the console display/keypad 18, which also assigns a corresponding function to be performed upon receipt of each of the valid identification codes. The learning process results in the storage of a set of valid identification codes mapped to specific functions for each wireless remote sensor 21 and wireless key 34 of the wireless security system 32 in the central control unit 12 of the wireless security system of the prior art illustrated in FIG. 2.
Despite the fact that the same identification code may be emitted by more than one wireless key (as found with automobile security systems where more than one wireless key provided to the purchaser of the automobile can control the security system), this is typically not the case with the majority of wireless security systems installed in commercial businesses and residential homes. Wireless keys 34 typically have two or more buttons which, although will emit the same identification code 34 upon being depressed, will emit different radio frequency messages differentiated in one or more status bits 40. Therefore, a significant problem is encountered in providing sufficient storage space to maintain the complete set of valid identification and status information mapped to functions for a wireless security system of any reasonable size. This problem is compounded by the fact that existing central control units 12 found in wireless security systems include only a very limited storage area for this type of information. Furthermore, in the case of wired security systems 10 without wireless capability, such as that illustrated in FIG. 1, there is understandably no such storage whatsoever. This problem is not present in conventional wired systems because such systems are not required to respond to radio frequency messages.
One solution to this problem has been to replace existing security systems with a unit that includes the wireless central receiver 15, wireless central transmitter 17, console display/keypad 18 and central control unit 12 including a larger identification code storage area in one unit. Such a unit must be placed near an access way to the secured building in order to provide an auxiliary means for the user to arm or disarm the system upon entering or leaving the premises as a failsafe backup to the wireless key 34. In addition, since the wireless central receiver is contained in the unit, the unit must be installed in a central location to facilitate adequate reception and transmission of radio frequency signals from the wireless remote sensors 21 and wireless key 34. However, a significant disadvantage results in that the unit, due to its location near an access or entry way, becomes particularly susceptible to destruction by an intruder before it has an opportunity to initiate an alarm condition. For this reason, many professional security installers are unwilling to install such a unit, preferring to keep the central control unit 12 physically separate from the receiver, transmitter and console. Furthermore, many users choose not to reinstall an entirely new unit due to the associated cost.
Therefore, it would be advantageous if a practical and affordable solution to interfacing with existing security systems could be designed which would supplement a limited or nonexistent storage area for identification codes already located in the central control unit while maintaining adequate reception and transmission of wireless radio frequency signals.
The spread of wireless technology in the,manufacture of security systems has been delayed significantly due to consumers' preference for wired systems. This is partially due to the vast quantity of wired security systems 10, such as that illustrated in FIG. 1, already in existence and partially due to various perceived disadvantages with wireless security systems, such as the need to replace batteries, poor reception and transmission of wireless signals, etc. Thus, the user having a wired security system 10 already installed without any wireless capability is not likely to install a wireless security system, even though he might benefit from the many advantages associated with a wireless security system such as the absence of wires as well as ease of installation, maintenance and upgrade. Likewise, many installers of security systems choose not to offer wireless security systems because of their relative inexperience with such systems in addition to the disadvantages already discussed.
Therefore, it would be advantageous if a method were developed whereby existing non-wireless ready wired security system could be retrofitted, thereby providing wireless capability to such units in an unobtrusive, inexpensive, and practical manner.
Many of the wireless security systems currently in use are limited in the number of identification codes 36 that can be recognized by the system. As illustrated in FIG. 2 and discussed above, the wireless key 34 is a common element in the typical wireless security system 32. The wireless key 34 may have four buttons, each initiating a different function within the wireless security system 10, such as arming/disarming of the system, opening a garage door, emergency alert and testing, via transmission of a unique radio frequency message in response to depression of a different button. For security purposes and ease of manufacture, each wireless key 34 will be designed to transmit a unique radio frequency message in response to depression of each button. Such a configuration can rapidly outpace the capacity for storage of valid identification and status information built into existing central control units 12.
Therefore, it would be advantageous if a method were developed which could supplement the number of wireless identification codes recognizable by an existing wireless security system in an efficient, unobtrusive and inexpensive manner.